Link budgets for AI connectivity
Optical transceivers have a defined link budget, which is the maximum amount of optical loss the link can tolerate while still operating reliably.
Every connector, patch panel, cassette, splice, and fiber segment adds insertion loss.
In large AI clusters, the limiting factor is often not distance. It is the accumulated loss from multiple connectors and patching stages.
If the link gets too close to the budget, the result can be:
- Higher FEC activity
- Increased pre-FEC errors
- Lower operating margin
- Intermittent link behavior
- Link failure in worst-case conditions
High performance margins for AI workloads
Cisco validates high-speed optics under demanding conditions that reflect complex AI cluster parameters.
The IEEE specifies a 3 dB link budget for 1.6T DR8 optics. For AI clusters, going beyond IEEE specification is a common requirement.
Cisco helps reduce deployment risk by testing our 1.6T optics with added insertion loss beyond IEEE specifications while maintaining very low error levels of only a few errors per codeword across every lane.
This is important in high-speed optics for AI because the link is built from multiple high-speed optical lanes. The link must perform reliably across all lanes, not just on average.
We have tested the Cisco 1.6T DR8 with up to 6.7 dB of insertion loss, while observing a maximum of 3 errors per codeword across each lane, indicating robust performance under stressed conditions.